1. Field of the Invention
This invention provides an intravascular DNA coated stent and methods for expressing recombinant genes in vivo using the DNA coated stent. DNA coated stents are useful for treating coronary and peripheral vascular diseases, particularly restenosis.
2. Background of the Invention
Coronary and peripheral angioplasty is routinely performed to treat obstructive atherosclerotic lesions in the coronary and peripheral blood vessels. Following balloon dilation of these blood vessels, 30-40% of patients undergo restenosis.
Restenosis is the reclosure of a peripheral or coronary artery following trauma to that artery caused by efforts to open a stenosed portion of the artery, such as, for example, by balloon dilation, ablation, atherectomy or laser treatment of the artery. Restenosis is believed to be a natural healing reaction to the injury of the arterial wall. The healing reaction begins with the thrombotic mechanism at the site of the injury. The final result of the complex steps of the healing process can be intimal hyperplasia, the uncontrolled migration and proliferation of medial smooth muscle cells, combined with their extracellular matrix production, until the artery is again stenosed or occluded. Thus, restenosis is characterized by both elastic recoil or chronic constriction of the vessel in addition to abnormal cell proliferation.
Currently restenosis must be treated with subsequent angioplasty procedures. In an attempt to prevent restenosis, metallic intravascular stents have been permanently implanted in coronary or peripheral vessels. For example, U.S. Pat. No. 5,304,122 (Schwartz et al.) describe metal stents useful for treating restenosis after balloon angioplasty or other coronary interventional procedures. The stent is typically inserted by catheter into a vascular lumen and expanded into contact with the diseased portion of the arterial wall, thereby providing mechanical support for the lumen. However, it has been found that restenosis can still occur with such stents in place; likely, because although the stent prevents elastic recoil of the artery, it fails to prevent the cell proliferation which leads to intimal hyperplasia. In addition, the stent itself can cause undesirable local thrombosis. To address the problem of thrombosis, persons receiving stents also receive extensive systemic treatment with anticoagulant and antiplatelet drugs.
Stents coated with various compositions have been proposed. For example, Dichek et al. (Circulation 1989, 80:1347-1353) describe coating stainless steel stents with sheep endothelial cells that had undergone retrovirus-mediated gene transfer for either bacterial xcex2-galactosidase or human tissue-type plasminogen activator. The stents were studied ex vivo in tissue culture dishes only. The feasibility of implanting the stents into arteries were not explored. This procedure of coating stents with cells is tedious, cumbersome and costly because cell have to be derived from a patient.
Other methods of providing therapeutic substances to the vascular wall by means of stents have also been proposed. For example, WO 91/12779, entitled xe2x80x9cIntraluminal Drug Eluting Prosthesis,xe2x80x9d and WO 90/13332, entitled xe2x80x9cStent With Sustained Drug Delivery,xe2x80x9d suggest coating stents with antiplatelet agents, anticoagulant agents, antimicrobial agents, anti-inflammatory agents, antimetabolic agents and other drugs to reduce the incidence of restenosis. Similarly, U.S. Pat. Nos. 5,571,166 and 5,554,182 (both to Dinh et al.) describe intraluminal stents coated with fibrin and heparin. The stent is used to treat restenosis.
Accordingly, one object of this invention is to provide an intravascular DNA coated stent.
A second object of this invention is to provide methods for expressing recombinant genes in vivo using the DNA coated stents.
A third object of this invention is to provide methods for treating coronary and peripheral vascular diseases, particularly restenosis and vein by-pass grafts, using the DNA coated stents.
The present inventors have now realized these and other objects through their discovery of methods for coating DNA on the outside surface of a stent.